The invention relates to a device for converting wind flow energy into mechanical energy, comprising a wind-engaging member connected to a base station by a load cable, a load cable storage means disposed at the base station, said storage means being configured to accommodate a section of the load cable, a control unit configured to veer out and haul in the load cable section cyclically from/into the load cable storage means, an energy converter configured to convert the energy from the wind flow force transferred from the wind-engaging member via the load cable, and the movement of the load cable section veered out from the load cable storage means into an electrical, thermodynamic or mechanical form of energy, a steering mechanism configured to produce a steered movement about a first axis or in a first direction of the wind-engaging member relative to the direction of airflow, a control unit configured to use the steering mechanism to bring the wind-engaging member, after the load cable section has been veered out, into a flight position associated with a low tensile force, and to bring the wind-engaging member, after the load cable section has been hauled in, into a flight position associated with a high tensile force.
Such a device is known from WO 00/40860. The basic principle of this notorious device is to allow a parachute to climb from a low position to a higher position while keeping the parachute horizontally offset above its anchoring point on the ground so that a high tensile force is produced in the guy cable of the parachute. This tensile force is used to drive a winch which serves as an attachment point for the parachute, with generators being driven by the rotation of said winch. After a certain length of the guy cable has been veered out, the parachute is steered into a position approximately vertical above the attachment point on the ground and/or the winch, thus minimizing the tensile force in the guy cable. The guy cable is then hauled in again by the veered-out length, then the parachute is steered into a horizontally offset position above the attachment point on the ground and the cycle starts anew. The difference between the energy generated by the generator when the rope is veered out and the energy that must be expended in order to haul in the rope results in the wind flow energy being converted into an electrical energy at the output of the generator.
This principle has a number of disadvantages which render its practical implementation difficult and which make it difficult to achieve an economical degree of efficiency.
A first disadvantage is that cyclical switching of the system between the generation and consumption of electrical energy occurs due to the cyclical manner of operation. On the one hand, this can cause variations which render it impossible to feed any electrical energy generated into public or private grids, for example. Another disadvantage of this cyclical switching is that the system routinely and repeatedly transitions from commencement of veering-out to a constant veering-out operation. Due to inertia of the system as a whole, the start-up operation can extend over a broad range of rope lengths, as a result of which various operating points are passed though in each cycle. Different cycles will also differ in respect of the veering speed, depending on which operating status the system is in when veering-out begins. Owing to these factors, it is impossible to adjust the generator in an economical manner to the convertible energy from the wind-engaging member. As a result, the efficiency of the system is reduced and the production costs of the system are increased.
Another disadvantage of the system is that economical operation is only possible when the length of guy cable veered out is large. However, this means large rope weights, which reduce the efficiency of the system. The large veered-out section of load cable also generates heavy wear of the guy cable, which results in overall deterioration in the efficiency of the system.